Underwater transducer and projector therefor

Abstract

An underwater transducer having both projector and hydrophone elements utilizes a new technique permitting the annular projector rings of a given piezoelectric material and resonant frequency to be tailored in diameter to accommodate various requirements, such as a need for more interior space. Where the projector rings can be expanded to the diameter of an accompanying hydrophone array, this makes possible a more compact and, in particular, a shorter structure than has been used for transducers of similar capability before. In the transducer the projector rings are positioned axially along a central support tube alternating with the hydrophones arranged in annular groups. Each projector ring is formed of a plurality of segments of alternately active material and inactive material having a sound velocity differing from (usually faster than) that of the active material. Thus the diameter of the annular elements for a given active material and a desired resonant frequency may be varied since the resonant frequency is related to the velocity of sound in the composite material used in the elements.

We claim: 
     
       1. An underwater transducer for projecting and receiving acoustic signals comprising: a container of generally cylindrical configuration containing electronic equipment;   a plurality of annular spacers of flexible material around the outside of said container and axially spaced from each other, each of said spacers having a plurality of outwardly facing recesses positioned around its periphery;   a group of piezoelectric hydrophone elements positioned in said recesses;   a plurality of annular projector elements spaced from said container and supported on said spacers, said projector elements being axially spaced from each other alternately with said groups of hydrophone elements, each said projector element comprising a plurality of alternate segments of active piezoelectric material and other material having a sound velocity greater than that of said active piezoelectric material.   
     
     
       2. An underwater transducer as set forth in claim 1 wherein said segments are bonded together with electrodes on the bonded surfaces of said active segments. 
     
     
       3. A underwater transducer as set forth in claim 1 wherein said active material is barium titanate and said other material is alumina. 
     
     
       4. An underwater transducer as set forth in claim 1 wherein said electronic equipment includes a transmitter connected to said projectors and receiving means connected to said hydrophone elements. 
     
     
       5. An underwater transducer for projecting and receiving acoustic signals comprising: a core section comprising a metal container of generally cylindrical configuration, said section containing electronic transmitting and receiving equipment;   a plurality of annular spacers of flexible material around the outside of said container and axially spaced from each other, each of said spacers including a plurality of recesses positioned around its periphery;   a group of piezoelectric hydrophone elements positioned in the recesses of each of said spacers;   a plurality of annular projector elements spaced from said container and supported on said spacers, said projector elements being axially spaced from each other alternately with said groups of hydrophone elements, each said projector element comprising a plurality of alternate segments of active piezoelectric material and inactive material having a sound velocity greater than that of the active material, said segments being bonded together and with electrodes on the bonded surfaces of said active segments.